Numerical Simulation of Influence of Buried Depth on Surrounding Rock Stability of Roadway

The stability of the surrounding rock of the roadway is critical to its excavation process and safe production [1-3]. Taking a mine in Shanxi as an example, this paper uses CDEM software to numerically simulate the surrounding rock stability of different buried tunnels, and discusses the buried depth effect of roadway surrounding rock stability.
1 numerical model construction
Based on the mechanical properties of surrounding rock and the geological conditions of the mine, a two-dimensional numerical model was constructed. The model adopts a fixed bottom method and two sides limit horizontal movement. In order to ensure that the original rock stress is a single variable, only one lithology is simulated, and there is no support after the roadway is excavated. In order to analyze the influence of the original rock stress change on the stability of surrounding rock, an arched roadway model was established. The roadway width is 4.6m, the height is 3.5m, the roadway area is 13.83m2, and the depth is 500,600,700 according to the depth. The 800m is taken from the original rock stress of 12.5, 15, 17.5, 20MPa, and the lateral pressure is 1.2MPa. The rock mechanics parameters of the roadway are shown in Table 1.

2 Influence of buried depth on surrounding rock stress of roadway
The stress distribution of the surrounding rock of the roadway corresponding to different buried depths is shown in Fig. 1. It can be seen from Fig. 1 that under the condition of shallow depth, the vertical stress and horizontal stress of the roadway are small. With the increase of the buried depth of the roadway, the original rock stress value of the roadway increases continuously, and the damage of the surrounding rock in the shallow roadway becomes more and more serious. The reduction of the bearing capacity causes the stress concentration zone to shift to the deep part, and the stress concentration value of the deep surrounding rock is getting larger and larger. It can be seen that the buried depth has a great influence on the stress distribution of the surrounding rock of the roadway. When the buried depth of the roadway is shallow, the stress concentration occurs at the bottom corner of the roadway. As the original rock stress increases, the concentrated area at the bottom corner of the roadway shifts to the deep. The range of stress concentration in the roadway is also larger.

3 Influence of original rock stress on displacement of surrounding rock of roadway

The vertical displacement field distribution of the surrounding rock of the roadway under different buried depth conditions is shown in Fig. 2(a). The horizontal displacement field distribution of the surrounding rock of the roadway is shown in Fig. 2(b), and the displacement of the roadway is shown in Fig. 3. It can be seen from Fig. 2 that there is a critical point in the influence of the buried depth of the roadway on the deformation of the surrounding rock of the roadway. When the buried depth of the roadway is 500-600 m, the average increase of the roof subsidence is 2. 71mm, the average increase of the two sets of approaching amount is 7.74mm, and the average increase of the bottom enthalpy is 6.45mm; 2 when the buried depth of the roadway is 700-800m, the sinking depth of the roadway is increased by 100m. The average increase is 3.92mm, the average increase of the two-way approaching amount is 9.03mm, and the average increase of the bottom enthalpy is 6.82mm; 3 when the tunnel depth is 700-800m, the roof roof sinking amount, two The amount of subsidence and the amount of bottom sill increased by 45% and 16% respectively when the depth of the tunnel was 400-600 m. 4 When the depth of the roadway exceeded 600 m, the increase of surrounding rock deformation increased with the increase of ground stress, and the deformation rate faster and faster. It can be seen from Fig. 3: 1 When the buried depth of the roadway is 500m, the surface displacement of the roadway is small. With the increase of the original rock stress, the surface displacement of the roadway increases slowly, and the amount of roof subsidence, the amount of bottom sill and the amount of movement of both gangs are small. 2 When the buried depth increases by 100 m, the average increase of the amount of roof subsidence is 3.42 mm, the average increase of the two sets of approaching amount is 8.51 mm, and the average increase of the bottom enthalpy is 6.67 mm.

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4 Influence of original rock stress on plastic zone characteristics of surrounding rock of roadway

The distribution of the surrounding plastic zone of the corresponding roadway under different buried depth conditions is shown in Fig. 4. The variation of the surrounding rock failure depth of the roadway under different buried depth conditions is shown in Fig. 5. It can be seen from Fig. 4 and Fig. 5 that the damage depth of the roadway floor is obviously larger than that of the roadway roof and the two gangs, and all of them increase with the increase of surrounding rock stress, and the plastic ring range is far from the increase of the original rock stress. The surface displacement of the roadway increases obviously with the original rock stress and gradually slows down. 2 When the original rock stress is small, the top and bottom of the roadway and the central and shallow surrounding rocks of the two tunnels first undergo tensile failure, with the surrounding rock stress of the roadway. When the bottom corner of the roadway begins to shear damage, the plastic zone of the roadway gradually becomes uniform, forming a relatively regular circular plastic ring, and then begins to develop deep, and the deep surrounding rock damage is shear failure; As the surrounding rock stress increases, the damage range of the top and bottom of the roadway increases from 2.5, 3.5m to 4,5.0m, and the damage of the roadway gang increases from 2.5m to 4m. In general, the original rock The increase of stress has more obvious influence on the damage range of the roadway.

5 Conclusion

(1) The buried depth has a great influence on the stress distribution of the surrounding rock of the roadway. When the buried depth of the roadway is shallow, the stress concentration occurs at the bottom corner of the roadway. As the original rock stress increases, the concentrated area at the bottom corner of the roadway goes deep. Transfer, roadway stress concentration
The scope is also larger.
(2) With the increase of in-situ stress, the increase of surrounding rock deformation increases with the increase of ground stress, and the rate of deformation increases gradually, indicating that the surrounding rock deformation of the roadway in the deep part of the mine will be sensitive with the increase of ground stress. Sexual enhancement.
(3) The increase of the original rock stress has obvious influence on the damage range of the two gangs.
references
[1] Zheng Yingren, Xu Hao, Wang Cheng, et al. Tunnel failure mechanism and deep and buried boundary standards [J]. Journal of Zhejiang University: Engineering Edition, 2010, 44(10): 1851-1856.
[2] Wang Xuebin, Pan Yishan, Tao Shuai. Simulation of shear strain localization process of circular tunnels of different sizes [J]. Chinese Journal of Geological Hazard and Control, 2009, 20(4): 101-108.
[3] Wang Yanli, Liang Liqi, Ji Chunlei. Stability analysis of surrounding rock of high buried depth underground cavern [J]. Haihe Water Conservancy, 2009 (6): 51-57.
Author: Yan Yuet; Shanxi Luan High River Energy Limited;
Article source: "Modern Mining"; 2016.8;
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